Solar control coatings having a layer stack of glass/Si3N4/NiCr/Si3N4 are known in the art, where the metallic NiCr layer is the sole infrared (IR) reflecting layer in the coating. In certain instances, the NiCr layer may be nitrided. For example, see U.S. Pat. No. 6,926,967, which is hereby incorporated herein by reference. See also U.S. Pat. No. 5,688,585.
Unfortunately, while such layer stacks with NiCr IR reflecting layers provide efficient solar control and are overall good coatings, they are lacking in terms of being able to achieve a wider palette of available colors when desired. For example, with such a coating stack, if bluish green is desired the approach is to significantly increase the bottom dielectric thickness which unfortunately results in undesirable interference effects in that particular coating.
Green coloration is often desired in the context of monolithic windows, insulating glass (IG) window units, and/or other suitable applications. Desirable green coloration (e.g., glass side reflective, or exterior), measured monolithically and/or in an IG window unit, may be characterized by: a* values of from −4.0 to −16.0, more preferably from −5.0 to −12.0, and most preferably −6.0 to −10.5; optionally in combination with b* values of from +7.0 to −15.0, more preferably from +3.0 to −8.0, and most preferably 0. to −5.0.
Low solar factor (SF) and solar heat gain coefficient (SHGC) values are also desired in some applications, particularly in warm weather climates. Solar factor (SF), calculated in accordance with EN standard 410, relates to a ratio between the total energy entering a room or the like through a glazing and the incident solar energy. Thus, it will be appreciated that lower SF values are indicative of good solar protection against undesirable heating of rooms or the like protected by windows/glazings. A low SF value is indicative of a coated article (e.g., IG window unit) that is capable of keeping a room fairly cool in summertime months during hot ambient conditions. Thus, low SF values are sometimes desirable in hot environments. While low SF values are sometimes desirable for coated articles such as IG window units, the achievement of lower SF values may come at the expense of sacrificing coloration. It is often desirable, but difficult, to achieve a combination of acceptable visible transmission, desirable glass side reflective coloration, and a low SF value for a coated article such as an IG window unit or the like. SF (G-Factor; EN410-673 2011) and SHGC (NFRC-2001) values are calculated from the full spectrum (T, Rg and Rf) and are typically measured with a spectrophotometer such as a Perkin Elmer 1050. The SF measurements are done on monolithic coated glass, and the calculated values can be applied to monolithic, IG and laminated applications.
U.S. Patent Document 2012/0177899 discloses several different coatings. Examples 2 and 5 on page four of US '899 are glass/SiN/NiCrNx/SiN/NiCrNx/SiN. However, these examples have undesirable bronze glass side reflective coloration. Examples 1 and 4 on page four of US '899 are glass/SiN/NiCrNx/SiN/NiCrNx/SiN, but with different thicknesses. Unfortunately, Examples 1 and 4 in US '899, while having desirable green coloration, suffer from undesirably high SF and SHGC values as well as high visible glass side reflectivity of 36%.
U.S. Pat. No. 8,286,395 discloses in Comparative Example 2 a coating as follows: glass/SiN/NbN/SiN/NbN/SiN. Unfortunately, Comparative Example 2 in U.S. Pat. No. '395 explains that the glass side reflective coloration is blue. Moreover, coating No. 2 in Comparative Example 1 of U.S. Pat. No. '395 also could not achieve green glass side reflective coloration, as evidenced by its external neutral a* color value of −1 (this is neutral color, not green color). Thus, green glass side reflective color could not be achieved with the materials/thicknesses of U.S. Pat. No. '395. U.S. Pat. No. '395 is also silent as to SF and SHGC values. It is noted that glass side reflective color is a significant color when an IG window unit is provided with the coating on surface two, as the glass side reflective color is the color seen by those outside viewing the building on which the window is mounted.
It would be desirable, for IG window units having two glass panes, if green glass side reflective coloration could be achieved in combination with a SF value of no greater than 0.29 (more preferably no greater than 0.25, and most preferably no greater than 0.23 or 0.21) and/or a SHGC value of no greater than 0.27 (more preferably no greater than 0.25, and most preferably no greater than 0.23), and optionally also in combination with one or more of: glass side visible reflectivity of no greater than 35% and/or heat treatability. Note that a typical conventional IG window unit with two panes has an SHGC value around 0.70. It would also be desirable for a coated article measured monolithically to have an SF value of no greater than 0.40 (more preferably no greater than 0.35 and most preferably no greater than 0.31) and an SHGC value of no greater than 0.42 (more preferably no greater than 0.38, and most preferably no greater than 0.36).
In certain example embodiments of this invention, it has surprisingly been found that by providing two or more IR reflecting layers (e.g., of or including NbZr and/or NbZrNx) between respective dielectric layers, along with particular thickness parameters, desirable green glass side reflective coloration can be achieved in combination with a low SF value. And optionally these desirable features may be achieved in combination with heat treatability and/or visible glass side reflectivity of no greater than 35% (more preferably no greater than 31%, and more preferably no greater than 27%, and sometimes no greater than 18%). Such coatings provide for improved color control and/or ranges when desired, low SF values and thus the ability to keep rooms cool in warm climates, and also for good thermal stability (low ΔE* value(s)) if desired.
Generally speaking, certain example embodiments of this invention fulfill one or more of the above listed needs by providing a coated article having green glass side reflective coloration and including a layer system supported by a glass substrate, the layer system comprising: a first dielectric layer comprising silicon nitride; a first infrared (IR) reflecting layer comprising NbZr on the glass substrate over at least the first dielectric layer comprising silicon nitride; a second dielectric layer comprising silicon nitride on the glass substrate over at least the first dielectric layer comprising silicon nitride and the first IR reflecting layer comprising NbZr; a second layer IR reflecting layer comprising NbZr on the glass substrate over at least the second dielectric layer comprising silicon nitride; a third dielectric layer comprising silicon nitride on the glass substrate over at least the second IR reflecting layer comprising NbZr; and wherein the coated article: has glass side/exterior reflective green coloration comprising a glass side/exterior a* value of from −4.0 to −16.0 and a glass side/exterior b* value of from +7.0 to −15.0; and (i) if measured monolithically has an SF value of no greater than 0.40 and an SHGC value of no greater than 0.42, and/or (ii) if an insulating glass (IG) window unit having two glass substrates/panes has an SF value of no greater than 0.25 and an SHGC value of no greater than 0.27. An additional IR reflecting layer and/or dielectric layer may be provided in certain example embodiments. The coated article may be a monolithic window unit, an IG window unit, or a laminated window unit in certain example embodiments of this invention.
Certain example embodiments of this invention fulfill one or more of the above listed needs by providing a coated article having green glass side reflective coloration and including a layer system supported by a glass substrate, the layer system comprising: a first dielectric layer comprising nitrogen; a first infrared (IR) reflecting layer on the glass substrate over at least the first dielectric layer; a second dielectric layer comprising nitrogen on the glass substrate over at least the first dielectric layer and the first IR reflecting layer; a second layer IR reflecting layer on the glass substrate over at least the second dielectric layer; a third dielectric layer comprising nitrogen on the glass substrate over at least the second IR reflecting layer; wherein each of the first and second IR reflecting layers comprises one or more of: NbZr, NbZrNx, NiCr, NiCrNx, NiCrMo, NiCrMoNx, NbCr, NbCrNx, Nb and NbNx; and wherein the coated article: has glass side/exterior reflective green coloration comprising a glass side/exterior a* value of from −4.0 to −16.0 and a glass side/exterior b* value of from +7.0 to −15.0; and (i) if measured monolithically has an SF value of no greater than 0.40 (more preferably no greater than 0.35, and most preferably no greater than 0.31) and an SHGC value of no greater than 0.42 (more preferably no greater than 0.38, and most preferably no greater than 0.36), and/or (ii) if an insulating glass (IG) window unit having two glass substrates/panes has an SF value of no greater than 0.25 (more preferably no greater than 0.23 and possibly no greater than 0.21) and an SHGC value of no greater than 0.27 (more preferably no greater than 0.25, and most preferably no greater than 0.23).
Thus, this invention covers monolithic window units, IG window units, laminated window units, and any other article including a glass substrate having a coating thereon as claimed. Note that monolithic measurements may be taken by removing a coated substrate from an IG window unit and/or laminated window unit, and then performing monolithic measurements. It is also noted that for a given coating the SF and SHGC values will be significantly higher for a monolithic window unit than for an IG window unit.
In certain example embodiments of this invention, heat treated (HT) coated articles have a glass side reflective ΔE* value due to heat treatment (e.g., thermal tempering) of no greater than 4.5, more preferably no greater than 4.0, even more preferably no greater than 3.5, and most preferably no greater than 3.0. For purposes of example, the heat treatment (HT) may be for at least about 5 minutes at a temperature(s) of at least about 580 degrees C., and is sufficient for thermal tempering. The term ΔE* is known in the art and is indicative of thermal stability upon heat treatment, and is defined and explained for example in U.S. Pat. No. 6,926,967 which is incorporated herein by reference.